<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8" />
		<title></title>
	</head>
	<body>
		<canvas id="canvas" style="border: 1px solid red;"></canvas>
		<button id="button">清除画面</button>
		<script>
			window.onload = function(){
				var canvas = document.getElementById("canvas");
				var cxt = canvas.getContext("2d");
				canvas.width =400;
				canvas.height =300;
				function airboard(){
				for(var i=0;i<5;i++){
					for(var j=0;j<6;j++){
						cxt.fillStyle = "rgb("+(255-100*i)+","+(255-100*j)+",200)";
						cxt.fillRect(25*i,25*j,25,25);
					}
				}
			}
				document.onclick=function(e){
					for (var i =0;i<5;i++){
						for(var j=0;j<6;j++){
							if(e.offsetX>=25*i&&e.offsetX<=25*i+25&&e.offsetY>=25*j&&e.offsetY<=25*j+25){
								cxt.strokeStyle= "rgb("+(255-100*i)+","+(255-100*j)+",200)";
								console.log(i,j);
								console.log("rgb("+(255-100*i)+","+(255-100*j)+",200)");
							}
						}
					}
				}
				var canvasx = canvas.getBoundingClientRect().left;
				var canvasy = canvas.getBoundingClientRect().top;
				console.log(canvasx);
				console.log(canvasy);
				canvas.addEventListener("mousedown",downfun);
				canvas.addEventListener("mousemove",movefun);
				canvas.addEventListener("mouseup",upfun);
				var startx;
				var starty;
				var endx;
				var endy;
				cxt.lineWidth=3;
				var offon=false;
				function downfun(e){
					offon=true;
					startx=e.clientX-canvasx;
					starty=e.clientY-canvasy;
				}
				function movefun(e){
					if(offon ==true){
					cxt.beginPath()
					endx=e.clientX-canvasx;
					endy=e.clientY-canvasy;
					cxt.moveTo(startx,starty);
					cxt.lineTo(endx,endy);
					cxt.stroke();
					cxt.closePath();
					startx=endx;
					starty=endy;
					console.log("1111");
					}
				}
				function upfun(){
					offon=false;
					cxt.closePath();
				}
				document.getElementById("button").onclick=function(){
					cxt.clearRect(0,0,canvas.width,canvas.height);
					airboard();
				}
			}
		</script>
	</body>
</html>

